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|  DSH 384% T ?( n2 N6 p# L7 [4 k# g
8 \ Q9 z+ @" v/ I2 B n* {2 o0 M
| Lithium Cell Protection+ H) g3 @" U& u/ G& [: T+ T7 ~
| 4.3.21, e/ V6 I3 h! F; b$ w
| 60950(ed.2)- Q; m) [. |: f7 o
|
1 {1 y; k( z; D; m4 w4 iStandard: IEC60950, 2nd Clause: 4.3.21 Sheet n. P384/ [( T% F3 t/ V# y8 X
Page 1(1)
& \: ~. ^ F6 O. p" OSubject: Lithium Cell Protection Key words:
, A9 E, Q( n* `2 L-Lithium Cell$ g) K) F& {0 V, ~, ?2 E
-Clearances
) j4 F. Q. y1 {2 W- failure mode
1 G3 h' X4 v6 Q: F& J' rProvisional Decision taken by ETF2" e: X7 P' ]6 E
and to be approved by CTL at its
; K2 B ~! d- B38th meeting, in Toronto" r# s1 _$ t7 U' Z) [
Question:2 F) g" j3 M! a# x+ M u
Clause 4.3.21 requires that two levels of protection are required to prevent forced or reversed charge# l; F+ p1 J# V
or forced discharge if this would result in a hazard. Conventionally a combination of resistor, diode
4 b: o% v& I6 o' l% `or ic has been considered suitable and is for the series current path. However, a new consideration
9 O: g8 [2 o& D9 I2 s* Ohas been raised in respect of adjacent tracks, separated by no more than operational insulation, which,
9 V0 q- T) ~! ]2 xunder s/c conditions will bypass the protective series components and provide charging current for& {3 F0 P, p, F: {& w5 I
either chargeable or non-rechargeable batteries. Does this mean that there is therefore a requirement l! n/ F- a$ G8 D
for Reinforced separation?
, u' U% y# x# B4 n: c' UIf that is the case, then the controlling factor is the clearance of 0.8mm in Table 5 (circuits not subject
! v. n& g3 s3 G& [to transient over voltage). This is based on the fact that creepage cannot be less than clearance and5 ~8 E' w8 v8 B, V/ b5 m
creepage can be calculated to be, for example at +5V, 0.4mm (based on rounding up 0.12mm to
1 N/ T% D! |# o! R- [$ o0.2mm for Basic and doubling for reinforced.2 b% K) y. Q) _/ n' {
Decision:
8 }* I6 ?9 z- x6 b7 ~& dOperational insulation is suitable taking into account 5.4.4 because there is no risk of electric shock.+ k5 J4 D6 H$ u. ?' r
(see 1.2.9.1)
7 D9 d# C+ g# S2 fCare should be taken by determining clearance and creepage distances which column of the table has% u9 k O; h2 d4 V1 j% i; A
to be used.(Transients have to be taken into account)
8 d: P3 [3 u. X$ E9 c$ ^# f# W- I+ E+ j G( G' E
6 r/ Y1 m6 J! D# {: l5 t% t |
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